Page 1 :
e Cryptands consist of three chains containing oxygen that are, connected by two nitrogen atoms. They can completely surround, (encapsulate) a metal ion of the appropriate size, coordinating to the, metal by a lone pair of electrons on each O atom and the two N, atoms., , e Like crown ethers, cryptands with different cavity sizes are highly, selective for metal ions of particular sizes., , e The number in the name of the cryptand is the number of oxygen, atoms in each strand of the molecule.e.g. 2, 2, 2-cryptand, , e Like crown ethers, cryptands are often used to dissolve simple, inorganic salts such as KMnOs in nonpolar organic solvents., , Complex of Alkaline Earth Metal, >» Smaller alkaline earth metals form complexes., , » Beryllium forms many complexes with mono, di and tetra dentate, ligands., , > Examples: [BeF3] , [BeFu]”, [Be (H2C20.)]”, [BeaO(R)s], where R may, be NO3 , HCOO , CH3COO etc., , , , Structure of [M(EDTA)]” Complex, where M= Mg,Ca